1. Field of the Invention
The present invention relates to an alternator for use in an automotive vehicle.
2. Description of Related Art
An alternator having a brush device including a slip-ring cover, along a circumferential direction of which an air passage is formed, has been known hitherto. An example of such an alternator is shown in JP-A-2002-359951. Water is prevented from entering portions around the slip-ring by making such an air passage.
However, in the conventional alternator, water entering through a rear cover is not prevented although water entering into the brush device composed of a brush holder and a slip-ring cover is suppressed. If a large amount of water enters through the rear cover, water may enter into the brush device through the air passage formed around the slip-ring cover, or the air passage may be closed by the water. When the air passage is closed, temperature around brushes may become high.